Adsorption of Methylene blue onto modified Agricultural waste

Abstract

Waste water discharged from industries contains dyes which prove danger to the ecology, affecting aquatic habitat and humans, due to that, different techniques on waste water treatment have been used throughout the years among which adsorption process triumphed, and this is due to low cost, high efficiency and controlled end product.

The aim of this work is to study the efficiency of modified kolanut pod (MKP) to adsorb methylene blue (MB) from aqueous solution. A batch process was carried out to study by optimizing, the effect of parameters such as contact time (10min to 180min), initial concentration (5mg/l to 150mg/l), adsorbent dosage (0.2g to 1g), temperature (303k to 333k), and pH (3 to 11). Characterization of the adsorbent was carried out using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), the results obtained showed a difference in the micrograph obtained before and after adsorption while the shifting and disappearance of peaks where also observed in the FTIR spectra respectively . Five isothermal models; the Langmuir, Freundlich, Dubinin-Radushkevich, Tempkin and Hasley were used to describe the adsorption process of which the data obtained best fit Freundlich and Hasley models. The kinetic studies revealed that adsorption of MB on to MKP follows pseudo second-order. The thermodynamic parameters obtained was a negative change in Gibbs Free energy which indicate spontaneity of the system, a positive change in Entropy which indicate a higher degree in randomness, and a high change in Enthalpy which suggest chemisorption. The collective results suggest MKP can be employed as a potential adsorbent for the removal of MB with 94% removal.